JP3333069B2 - Charging member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic apparatus, and more particularly, to a charging member having an elastic layer mainly composed of epichlorohydrin rubber formed on a conductive support.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger has been widely used as a charging method for uniformly charging the entire surface of a photosensitive member. This corona discharger is effective as a means to uniformly charge the photoreceptor to a certain potential. Conversely, charging by corona discharge requires a high-voltage power supply, The generation of ozone and the generation of a large amount of ozone not only adversely affect the environment but also deteriorate the charging member and the photoreceptor due to the ozone.

[0003] On the other hand, a contact roller charging system in which a charging roller (charging member) is brought into contact with a photosensitive member and a voltage is applied while being driven to rotate to charge the surface of the photosensitive member is disclosed in Japanese Unexamined Patent Publication No. Sho.
It is disclosed in Japanese Unexamined Patent Publication No. 3-167380, “AC induction charging device”. According to JP-A-63-167380,
Compared with the corona discharge method, it has the advantages of lowering the voltage of the power supply and generating less ozone, but is inferior in terms of charging uniformity.

In order to improve the uniformity of the charging, for example, in the “contact charging method” disclosed in Japanese Patent Application Laid-Open No. 63-149668, twice the charging start voltage when a DC voltage is applied. It is disclosed that by superimposing an AC voltage having the above-mentioned peak-to-peak voltage, charging uniformity can be considerably improved. However, in the contact charging method in which charging is performed by applying a voltage obtained by superimposing an AC voltage and a DC voltage, an unpleasant environment is given as a charging noise due to mechanical vibration caused by the AC voltage of the charging device. In addition, a large amount of the alternating current consumes a disadvantage that the reduction of ozone generation is impaired.

[0005] These disadvantages can be solved by applying only a DC voltage to the charging device to perform charging.
There is a problem that it is difficult to obtain uniform charging. For this reason, according to Japanese Patent Application Laid-Open No. Hei 5-341627, uniformity of charge and withstand voltage are improved by using epichlorohydrin rubber, which is semiconductive by itself, for the elastic layer of the charging member (charging roller). Have been.

[0006]

However, according to the charging member in which the elastic layer mainly composed of epichlorohydrin rubber is formed on the conventional conductive support, the non-adhesive surface is formed on the semiconductive elastic layer. Although a layer is formed, when used as a charger in a copier for a long time, residual toner particles that pass through the cleaning unit and remain on the photoreceptor adhere to the surface of the charging member that is in contact with the photoreceptor However, since toner, paper powder, and the like adhere to the surface of the charging member, there is a problem that the electrical resistance of the charging member is increased and the charging performance is reduced. In other words, there is a problem that the durability of the charging member is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to improve the durability of a charging member by suppressing adhesion of toner, paper powder, and the like to the surface of the charging member. .

[0008]

According to a first aspect of the present invention, there is provided a charging member according to a first aspect of the present invention, wherein an elastic layer mainly composed of epichlorohydrin rubber is formed on a conductive support. A surface layer containing a polymer obtained by curing a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with isocyanate is formed on the layer.

According to a second aspect of the present invention, there is provided a charging member in which an elastic layer mainly composed of epichlorohydrin rubber is formed on a conductive support, wherein a fluoroolefin and a hydroxyl group-containing vinyl ester are formed on the elastic layer. This is a polymer-containing surface layer formed by curing a copolymerized solvent-soluble polymer with melamine.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the charging member of the present invention will be described in the form of a charging member of the present invention and a configuration example of a charging device using the charging member of the present invention. This will be described in detail with reference to FIG.

First, an example of the shape of the charging member of the present invention will be described. The charging member of the present invention has, for example, a roller shape as shown in FIG.
It comprises a semiconductive elastic layer 102 provided around the conductive support 101 and a surface layer 103 formed on the outer peripheral surface of the semiconductive elastic layer 102.

In FIG. 1, the conductive support 1
01, an adhesive layer for improving the adhesiveness between the semiconductive elastic layer 102 and the surface layer 103 may be provided. For example, the conductive support 101 may be treated with a conductive primer such as synthetic rubber mixed with a conductive substance such as carbon black.

As the conductive support 101, a conductive resin such as a metal such as iron, stainless steel, and aluminum, a resin dispersed with carbon black, and a resin dispersed with metal particles can be used.

Good results can be obtained when the electric resistance of the semiconductive elastic layer 102 is in the range of 10 ⁷ to 10 ⁹ Ω · cm. Therefore, polar rubbers such as epichlorohydrin rubber, nitrile rubber, urethane rubber, chloroprene rubber, and acrylic rubber can be used. Among them, the rubber itself has relatively low electric resistance, and furthermore, environmental fluctuations may occur. Because of its small size, epichlorohydrin rubber is used.

Further, epichlorohydrin rubber (abbreviation: E
CO) is a homopolymer of ECO, a copolymer of ECO and ethylene oxide (abbreviation: EO), a copolymer of ECO and allyl glycidyl ether (abbreviation: AGE), EC
Terpolymer of O, EO and AGE (abbreviation: GECO)
Among them, GECO is preferred because of its relatively low electric resistance and small environmental fluctuation (that is, low environmental dependency).

The thickness of the semiconductive elastic layer 102 is
Good results are obtained in the range of 0.5 to 10 mm. The reason for this is that if the thickness of the semiconductive elastic layer 102 is less than 0.5 mm, the photoreceptor will not only break down the insulation or become unstable, but if there is a pinhole in the photoreceptor, the portion will be damaged. The current is concentrated on the surface and leakage is likely to occur.
Horizontal streaks appear on the image. On the other hand, if the thickness of the semiconductive elastic layer 102 is more than 10 mm, the charging efficiency is reduced, and a higher voltage needs to be applied. As a result, the amount of ozone generated increases.

On the outer peripheral surface of the semiconductive elastic layer 102, a non-adhesive film having a thickness of 1 to 20 μm is formed as a surface layer 103. The surface layer 103 is formed for the purpose of suppressing adhesion of toner and the like to the surface of the charging member and maintaining good charging characteristics for a long period of time.

For this purpose, the semiconductive elastic layer 102
The surface layer 103 containing a polymer obtained by curing a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with isocyanate or melamine is used as a non-adhesive material formed on the surface of the polymer.

The material constituting the surface layer 103 is the surface layer 1
In order to adjust the entire surface layer 103 to the semiconductive elastic layer 102 using the polymer used in the base material 03 as a base, a conductive rubber composition such as epichlorohydrin rubber, nitrile butadiene rubber, chloroprene rubber, or carbon black, zinc oxide It can be formed by appropriately adding a conductive fine powder such as tin oxide, titanium oxide, or the like. Among them, a conductive rubber composition is preferable as the resistance adjuster from the viewpoint of uniformity of electric resistance.

The thickness of the coating of the surface layer 103 is 1-2.
0 μm, particularly preferably 5 to 10 μm.

Note that the resistance value of the surface layer 103 is 1 × 10 ⁸
When the resistance is less than Ω · cm, it is not preferable because the pressure resistance cannot be obtained when the photosensitive drum is damaged, and 1 × 10 ¹¹
Above Ω · cm, it is difficult for current to flow, and charging failure may occur.

At present, the solvent-soluble polymer which is the base material of the polymer used for the surface layer 103 includes a fluoroolefin hydroxyl group-containing vinyl ester copolymer and a fluoroolefin hydroxyl group-containing vinyl ether copolymer. From the viewpoints of non-adhesion to toner, compatibility with conductive rubber composition, dispersibility of conductive fine powder, and little change in liquid viscosity (thickening) over time when formed into a paint, It has been found that the fluoroolefin hydroxyl group-containing vinyl ester copolymer is superior.

Configuration Example of Charging Device Using Charging Member of the Present Invention Next, a configuration of a charging device using the charging member will be described with reference to FIG. In the figure, reference numeral 201 denotes a charging member of the present invention, in which the roller-shaped charging member shown in FIG. 1 is used. 202 denotes a charging member 201
1 shows a DC power supply for applying a DC voltage to the metal core of FIG.

FIG. 2 shows an example in which the charging device of the present invention is applied to an electrophotographic apparatus. In this electrophotographic apparatus, a charging member 20 is provided around a drum-shaped electrophotographic photosensitive member 203.
1, an image exposure device (not shown), a developing means 204, a transfer charging device 205, a cleaning device 206, and a pre-exposure device (not shown) are arranged. In the figure,
Reference numeral 207 denotes exposure light emitted from the image exposure device, 208 denotes pre-exposure light of the pre-exposure device, and 209 denotes a member to be transferred such as paper.

For example, an electrophotographic photosensitive member 203 such as an OPC
A voltage (for example, 1.5 KV) is applied by the DC power supply 202 to the core metal of the charging member 201 which is disposed in contact with the upper part,
The surface of the electrophotographic photosensitive member 203 is charged, and an image on an original is image-exposed to the electrophotographic photosensitive member 203 by an image exposure device to form an electrostatic latent image.

Next, the electrostatic latent image on the electrophotographic photosensitive member 203 is developed by attaching the developer in the developing device 204 to the electrophotographic photosensitive member 203, and the developing agent on the electrophotographic photosensitive member 203 is further developed. The transfer agent is transferred to the transfer member 209 such as paper by the transfer charging device 205, and the cleaning device 20
6, the electrophotographic photosensitive member 2 is not transferred to paper at the time of transfer.
The developer remaining on 03 is collected. If residual charge remains on the electrophotographic photosensitive member 203, the charging member 2
Before performing the temporary charging by 01, it is better to remove the residual charge of the electrophotographic photosensitive member 203 by a pre-exposure device.

The course up to the present invention has been described above by describing the shape and configuration example of the charging member of the present invention and the configuration example of the charging device using the charging member of the present invention. The charging uniformity of the charging member 201 of the present invention, which seeks to obtain uniform charging only by using a conventional charging roller (for example, Japanese Unexamined Patent Publication No.
The electrical characteristics (R, C) and the layer configuration of the rollers are naturally greatly different from those in JP-A-4-73364 and JP-A-7373367. In other words, the AC voltage superposition type consists of a conductive elastic layer (rubber in which conductive particles such as carbon black are dispersed) and a surface resistance layer. Since the surface resistance layer functions as a capacitor, the capacitance is large. The effect of making the charged potential uniform by superimposition is large.

On the other hand, in the DC voltage only type of the present invention, the roller layer functions as a resistor (ie,
(Since the capacitance is small), even if the AC voltage is superimposed, it hardly contributes to uniform charging.

Embodiments 1 to 3 Hereinafter, the charging member of the present invention will be described in the order of [Embodiment 1], [Embodiment 2], and [Embodiment 3] with reference to the drawings.

[Embodiment 1] In Embodiment 1, a charging member is prepared by the following method. First, a stainless steel core of φ8 mm is used as the conductive support 101. Next, the semiconductive elastic layer 102 is formed with the following composition. GECO-based epichlorohydrin (trade name: Epichroma CG102, manufactured by Daiso) 100 parts by weight Light calcium carbonate 30 parts by weight Sub (trade name: GT, manufactured by Tenma Sub Chemicals) 10 parts by weight Zinc flower 5 parts by weight Stearic acid 0.5 parts by weight Vulcanization accelerator (trade name: Noxeller TT, manufactured by Ouchi Shinko Chemical) 1.0 parts by weight Vulcanization accelerator (trade name: Noxeller DM, manufactured by Ouchi Shinko Chemical) 1.5 parts by weight Vulcanization accelerator (trade name) : Barnock R, manufactured by Ouchi Shinko Chemical) 1.0 part by weight Vulcanizing agent (trade name: Sulfax, manufactured by Tsurumi Chemical) 0.25 part by weight

After kneading the above-mentioned compound to form a compound having a uniform composition, primary vulcanization (mold forming method: 150 ° C. × 1) is performed on a φ8 mm stainless steel core (conductive support 101).
5 minutes), secondary vulcanization (molding method: 155 ° C x 7 hours)
Accordingly, a roller-shaped semiconductive elastic layer 102 having an outer diameter of 14 mm was provided. The volume resistance of this elastic roller is 2 × 1
0 ⁷ Ω · cm and the roller rubber hardness was 38 degrees (JisA).

The measurement of the volume resistance of the roller is as follows.
° C, 60% R.C. After leaving in the environment of H for 16 hours, 2
5.4mm width copper foil tape (trade name: Scotch No. 1)
181 and 3M) are wound around the circumference of the roller to form an electrode, a direct current of 1 KV is applied between the roller core and the electrode, and the current value one minute after that is measured, and the resistance between the core and the electrode is measured. The value was determined. The rubber hardness of the roller was measured using JisK63.
Using a hardness meter JisA described in No. 01, the pressure was measured perpendicular to the center axis direction of the roller.

Next, a surface layer 103 was formed on the semiconductive elastic layer 102 as follows. First, the coating liquid for the surface layer was prepared as follows. 100 parts by weight of fluoroolefin hydroxyl group-containing vinyl ester copolymer (trade name: Zafflon FC-110, manufactured by Toagosei Chemical Industry), 11 parts by weight of isocyanate curing agent (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry), toluene / xylene =
500 parts by weight of 1/1 mixed solvent was sufficiently stirred to obtain a uniform solution, which was designated as solution A.

Solution A A polymer solution for adjusting the electric resistance of the base material was prepared as follows. GECO-based epichlorohydrin (trade name: Epichroma CG102, manufactured by Daiso) 1
100 g is masticated for about 15 minutes with an 8-inch double roller to increase the plasticity of the epichlorohydrin raw rubber.
The subsequent organic solvent treatment was facilitated.

Toluene / 4-methyl-2-pentanone =
To 100 parts by weight of a 1/1 mixed solvent was added 5 parts by weight of the above masticated epichlorohydrin raw rubber, and the mixture was sufficiently stirred to dissolve the raw rubber to prepare an epichlorohydrin solution.

Next, 40 parts by weight of the epichlorohydrin solution was added to 100 parts by weight of the solution A, and the mixture was sufficiently stirred to obtain a surface layer paint. Table 1 shows the results obtained by measuring the liquid adhesion of the surface layer paint immediately after the adjustment and after 24 hours. The viscosity was measured using a B-type viscometer (manufactured by Tokyo Keiki) at a liquid temperature of 25 ° C.

Further, after the dip coating is performed on the semiconductive elastic layer 102 using the surface layer coating,
The coating film was cured at 0 ° C. for 2 hours to form a surface layer 103 having a thickness of 6 μm. The charging roller (charging member)
Table 1 shows the results of measuring the volume resistance of the sample.

The charging roller (charging member) manufactured as described above is used as a regular development type copier FT5500 (manufactured by Ricoh).
A photoconductor (OP) is installed instead of the primary corona charger.
C) The drum was rotated in contact with the drum surface.
A DC voltage of -1.4 KV is applied as a primary charging voltage, and 2
4 ± 1 ° C., 50-55% R.C. The apparatus was continuously operated in the environment of H, and the potential of the dark potential of the photoreceptor was initially measured every 5,000 sheets and every 10,000 sheets, and the contamination state of the charging roller surface and the image quality were measured and evaluated.

Table 1 shows the results of the above measurements and evaluations.
The state of contamination of the surface of the charging roller with toner and the like was evaluated according to the following criteria. Double circle: A small amount of toner or the like is attached, but the attached matter on the roller surface can be easily wiped off with a cloth or the like. ：: Toner is slightly left on the roller surface after wiping. Δ: Complete wiping was not possible, and a thin film such as toner remained on the roller surface. X: The toner and the like are strongly fixed to the roller surface.

[0040]

[Table 1]

Example 2 A surface layer 103 was formed on a semiconductive elastic layer 102 as in Example 1 as follows.
First, the coating liquid for the surface layer was prepared as follows. Fluoroolefin hydroxyl group-containing vinyl ester copolymer (trade name: Zafflon FC-110, manufactured by Toa Gosei Chemical Industry) 10
0 parts by weight, 28 parts by weight of a methylated melamine curing agent (trade name: Sumidur M-40S, manufactured by Sumitomo Bayer Urethane), and 500 parts by weight of a mixed solvent of toluene / xylene = 1/1 are sufficiently stirred to obtain a uniform solution. This was designated as solution B.

B solution The same epichlorohydrin solution as in Example 1 was used as a polymer solution for adjusting the electrical resistance of the base material. 35 parts by weight of the epichlorohydrin solution was added to 100 parts by weight of the B solution, and the mixture was sufficiently stirred to obtain a coating for the surface layer.

After the surface layer paint was applied on the semiconductive elastic layer 102 in the same manner as in Example 1, the paint was applied at 170 ° C.
The coating is cured in × 2 hours, and the surface layer 10 having a thickness of 7 μm is cured.
3 was formed.

Table 1 shows the results of measurement and evaluation of the liquid viscosity of the coating material for the surface layer and the charging roller (charging member) in the same manner as in Example 1.

Example 3 A surface layer 103 was formed on a semiconductive elastic layer 102 similar to that of Example 1 as follows.
First, the coating liquid for the surface layer was prepared as follows. Fluoroolefin hydroxyl group-containing vinyl ester copolymer (trade name: Zafflon FC-110, manufactured by Toa Gosei Chemical Industry) 10
0 parts by weight, butylated melamine curing agent (trade name: Superbecamine L-117-60, manufactured by Dainippon Ink and Chemicals, Inc.)
25 parts by weight, a mixed solvent of toluene / xylene = 1/1 5
00 parts by weight was sufficiently stirred to obtain a uniform solution.
The solution was used.

The same epichlorohydrin solution as in Example 1 was used as a polymer solution for adjusting the electric resistance of the C solution base material. 37 parts by weight of the epichlorohydrin solution was added to 100 parts by weight of the C solution, and the mixture was sufficiently stirred to obtain a surface layer paint.

After the surface layer paint was applied on the semiconductive elastic layer 102 in the same manner as in Example 1, the paint was applied at 170 ° C.
The coating is cured in × 2 hours, and the surface layer 1 having a thickness of 10 μm
03 was formed.

Table 1 shows the results of measurement and evaluation of the liquid viscosity of the surface layer paint and the charging roller (charging member) in the same manner as in Example 1.

[Comparative Example 1] Here, Comparative Example 1 was prepared as a comparative example as follows. Table 1 shows the results of evaluating the roller having only the semiconductive elastic layer 102 of Example 1 in the same manner as in Example 1.

[Comparative Example 2] Here, Comparative Example 2 was prepared as a comparative example as follows. A surface layer 103 was formed on a semiconductive elastic layer 102 similar to that in Example 1 as follows. First, the coating liquid for the surface layer was prepared as follows. Fluoroolefin hydroxyl group-containing vinyl ether copolymer (trade name: Lumiflon LF601C main agent, manufactured by Asahi Glass) 1
00 parts by weight, 9 parts by weight of an isocyanate curing agent (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 500 parts by weight of a mixed solvent of toluene / xylene = 1/1 are sufficiently stirred to form a uniform solution. The solution was used.

D Solution The same epichlorohydrin solution as in Example 1 was used as a polymer solution for adjusting the electrical resistance of the base material. 40 parts by weight of the epichlorohydrin solution was added to 100 parts by weight of the D solution, and the mixture was sufficiently stirred to obtain a coating for the surface layer.

After this surface layer paint was applied on the semiconductive elastic layer 102 in the same manner as in Example 1, the paint was applied at 100 ° C.
The coating film is cured in × 2 hours, and the surface layer 10 having a thickness of 8 μm is cured.
3 was formed.

Table 1 shows the results of measurement and evaluation of the liquid viscosity of the surface layer paint and the charging roller (charging member) in the same manner as in Example 1.

Comparative Example 3 Here, Comparative Example 3 was prepared as a comparative example as follows. A surface layer 103 was formed on a semiconductive elastic layer 102 similar to that in Example 1 as follows. First, the coating liquid for the surface layer was prepared as follows. 100 parts by weight of a fluoroolefin hydroxyl group-containing vinyl ether copolymer (trade name: Lumiflon LF601, manufactured by Asahi Glass), a methylated melamine curing agent (trade name: Cymel 30)
3, Mitsui Cyanamid) 16 parts by weight, toluene /
500 parts by weight of a mixed solvent of xylene = 1/1 was sufficiently stirred to obtain a uniform solution, which was used as an E solution.

E Solution The same epichlorohydrin solution as in Example 1 was used as a polymer solution for adjusting the electric resistance of the base material. To 100 parts by weight of the E solution was added 42 parts by weight of the epichlorohydrin solution, and the mixture was sufficiently stirred to obtain a coating for the surface layer.

After the surface layer paint was applied on the semiconductive elastic layer 102 in the same manner as in Example 1, the paint was applied at 170 ° C.
The coating film is cured in × 2 hours, and the surface layer 10 having a thickness of 6 μm is cured.
3 was formed.

Table 1 shows the results of measurement and evaluation of the liquid viscosity of the coating material for the surface layer and the charging roller (charging member) in the same manner as in Example 1.

As is apparent from Examples 1 to 3 and Comparative Examples 1 to 3, as described above, the non-adhesiveness to toner and the charging characteristics by using the charging member of the present invention by applying a DC voltage. Can substantially maintain the initial characteristics over a long period of time. That is, it is possible to improve the durability of the charging member by suppressing adhesion of toner, paper powder, and the like to the surface of the charging member for a long period of time, and to obtain stable image characteristics (that is, image quality). .

Further, the coating material for the surface layer forming the surface layer 103 has a small change in the liquid viscosity over time.
When mass-producing the charging roller (charging member), the surface layer 103
The thickness of the (coating film) can be made uniform. That is, it is easy to manage the mass production of the charging roller (charging member).

[0060]

As described above, the charging member of the present invention (claim 1) is obtained by curing a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with an isocyanate on the elastic layer. Since the surface layer containing the polymer to be formed is formed, the non-adhesiveness of the charging member surface is improved, so that toner and paper dust are prevented from adhering to the surface of the charging member, and the charging characteristics are stable over a long period of time. Will be obtained. That is, good output image quality can be maintained over a long period of time.

Further, since the viscosity of the liquid for the surface layer changes little with time, for example, when mass-producing a charging roller (charging member), the thickness of the surface (coating film) of the elastic layer can be made uniform. That is, management of mass production of the charging roller (charging member) becomes easy.

Further, the charging member of the present invention (Claim 2) is
Since a surface layer containing a polymer obtained by curing a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with melamine is formed on the elastic layer, the non-adhesiveness of the charging member surface is improved. Adhesion of toner, paper powder, and the like to the surface of the charging member is suppressed, and stable charging characteristics can be obtained over a long period of time.
That is, good output image quality can be maintained over a long period of time.

Further, since the change in the liquid viscosity of the paint for the surface layer with the passage of time is small, for example, when mass-producing a charging roller (charging member), the thickness of the surface (coating film) of the elastic layer can be made uniform. That is, management of mass production of the charging roller (charging member) becomes easy.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a shape and a configuration example of a charging member of the present invention.

FIG. 2 is an explanatory diagram showing a configuration example of a charging device using the charging member of the present invention.

[Explanation of symbols]

 Reference Signs List 101 conductive support 102 semiconductive elastic layer 103 surface layer 201 charging member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/08 F16C 13/00 G03G 15/16 103

Claims (2)

(57) [Claims] 1. A charging member in which an elastic layer mainly composed of epichlorohydrin rubber is formed on a conductive support, wherein a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with isocyanate on the elastic layer. A charging member having a surface layer containing a polymer obtained by curing. 2. A charging member having an elastic layer mainly composed of epichlorohydrin rubber formed on a conductive support, wherein a solvent-soluble polymer obtained by copolymerizing a fluoroolefin and a hydroxyl group-containing vinyl ester with melamine is formed on the elastic layer. A charging member having a surface layer containing a polymer obtained by curing.